Endometriosis affects 5 1/2 million reproductive age women and girls in the USA and Canada, and millions more worldwide, causing pelvic pain and infertility. Diagnosis and treatment require costly, invasive surgery to identify and ablate ectopic endometrial tissue. Endometriosis is one of the three top reasons for hysterectomy in the USA; over 1/2 million hysterectomies are performed annually at an estimated cost of more than $5 billion. Yet, the pathogenesis of endometriosis remains poorly defined. The long-term objectives of this research are to develop novel methods of medical management by characterizing endometriotic secretory proteins that correlate with the cellular and molecular pathogenic mechanisms of endometriosis. This research evolves from the discovery that endometriotic lesions actually synthesize and secrete haptoglobin (Hp). Intriguingly, endometriotic haptoglobin (eHp) is differentially glycosylated compared to hepatic Hp. Preliminary data support a pathologically relevant role for eHp in the aberrant immunological phenomena that support the disease process in women with endometriosis. The hypothesis to be tested is that by expressing eHp, endometriotic tissues from women with endometriosis avoid phagocytic eradication while stimulating peritoneal macrophage inflammatory cytokine secretion. In turn, the macrophage cytokines increase endometriotic tissue eHp production, creating a local, feed-forward loop between ectopic endometrium and macrophages favoring the establishment of endometriosis. To test this hypothesis, peritoneal macrophages, and endometriotic lesions when present, will be collected from women without and with endometriosis. These immune cells and tissues will be used to investigate three specific aims: 1) Identify the effects of eHp on peritoneal macrophage phagocytosis by analyzing the five steps of macrophage function in vitro including chemotaxis, adherence, ingestion, oxidative metabolism and activation. 2) Characterize a ligand/receptor mechanism whereby eHp causes aberrant macrophage function, by selectively altering eHp glycans and/or blocking peritoneal macrophage integrins. 3) Quantify the effects of macrophage inflammatory cytokines and growth factors on eHp synthesis and secretion. These experiments will provide insight into the pathogenesis of endometriosis by determining if endometriotic tissues, peritoneal macrophages or both are responsible for this pathology, if this mechanism is unique to women with endometriosis and confirm our feedforward hypothesis. As a result, novel non-invasive strategies for early detection and innovative treatment of endometriosis may be developed that markedly reduce the health burden of this malady.